Gen. James Mattis, commander of U.S. Central Command, is accelerating a military buildup around the Persian Gulf, with new provisions added to parry possible Iranian military moves and to strike at targets inside Iran if necessary. This buildup comes just as a suicide bomb attack in Bulgaria on July 18 killed five Israeli tourists. In a statement, Israeli Prime Minister Benjamin Netanyahu said, "This is a global Iranian terror onslaught and Israel will react firmly to it." Whether this bombing will result in Israeli military action against Iran remains to be seen. What is clear is that Mattis wants his forces in the region ready for that event.

Military planners at the Pentagon seem to be granting Mattis most, but not all, of his requests for reinforcements. Giving the general what he wants right now is not cost-free, however, and comes with its own set of risks. Now that the Pentagon has agreed to step up its commitment of air and naval power to deter Iran, the question becomes whether planners will be able to sustain such a commitment to an open-ended problem while the Pacific is making its own growing demands for U.S. air and naval assets. If not, the Pentagon will have to come up with alternate ways of sustaining Mattis’s requirements while meeting growing demands for ships and aircraft in Asia. If the tensions in the Gulf continue to mount, the planned "pivot" to the Pacific may have to be indefinitely postponed.

The U.S. military buildup in the Persian Gulf took on a new dimension in late April when the U.S. Air Force revealed the arrival of an undisclosed number of F-22 stealth fighters at the Al Dhafra air base in the United Arab Emirates. On June 23, four U.S. Navy minesweeping ships arrived in the Persian Gulf, doubling the Navy’s minesweeping force there. To support the beefed-up minesweeping squadron, and to support maritime special operations missions, the Navy has positioned USS Ponce in the Gulf, an amphibious assault ship now reconfigured as an "afloat forward staging base." In September, the Navy and about 20 other countries will conduct an 11-day minesweeping exercise near the Gulf, a display no doubt aimed at deterring the military decision-makers in Tehran from any thought of trying to close the Strait of Hormuz.

Missile defense is also receiving stepped-up attention. Qatar has agreed to host a long-range X-band missile defense radar site, adding to similar sites the United States already operates in Israel and Turkey. The radar in Qatar will peer deep into Iran and will give the U.S. missile defense command network an earlier alert of possible Iranian missile launches. The missile defense command system will share the data received from the Qatar radar with missile interceptors based on Navy ships and with land-based interceptor batteries around the region.

Finally, Defense Secretary Leon Panetta personally approved Mattis’s request for an early deployment of the USS John C. Stennis aircraft carrier strike group. The Stennis group returned to Bremerton, Washington in March from a long Middle East deployment. Panetta’s order will send the group back in late summer and will cut four months off the time the crews expected to be back home. The Stennis was supposed to sail this winter for service in the Pacific Command region. Instead, it will replace USS Enterprise (which is heading for retirement) on station in the Arabian Sea and will provide Mattis with the uninterrupted presence of two aircraft carriers in his region.

The rapid turnaround of the Stennis group shows the Navy’s ability to respond to urgent requests. However, neither the Navy’s ships nor its crews can maintain this operational tempo as a routine practice. The Stennis and her escort vessels will not receive all of the between-deployment maintenance they require and sending the crews back out on another long deployment after only five months back will be demoralizing.

Pentagon spokesman George Little said that the Stennis’s accelerated deployment is not aimed at any specific threat nor is it a direct response to tensions with Iran. Negotiations with Iran over its nuclear program have reached an undeclared impasse, raising the likelihood that Israel will see the need for a preemptive strike against Iran’s nuclear complex — a long-standing concern that the Bulgaria attack may aggravate. If war breaks out over Iran sometime during the remainder of 2012, Mattis wants Iran’s leaders to know that he has his own forces in position to both parry possible retaliation and to retaliate inside Iran if necessary.

Mattis is making prudent preparations for a possible contingency. But conflict remains hypothetical, which leaves Iran as an open-ended problem that Mattis and his successors at Central Command will have to manage for some undefined period. In that case, instituting what are essentially wartime deployment practices, such as Panetta’s early deployment order to the Stennis group, for the management of an open-ended problem is convincing evidence that the Navy is too small for the responsibilities policymakers are heaping on it.

Maintaining a continuous deployment of two aircraft carriers in the Arabian Sea, in a manner that won’t ruin the ships or drive sailors out of the Navy, requires committing six to seven carriers to the task. Such an allocation is required in order to establish a sustainable rotation schedule. With Enterprise’s retirement, the Navy will have only 10 carriers until the new aircraft carrier USS Gerald R. Ford arrives in service in 2015. Under the current shipbuilding plan, the carrier fleet will then stay at 11 ships thereafter.

This will leave four to five carriers for all other responsibilities, including the Pacific Command area, which is universally considered to be the theater most suited for air and naval power — and the region where the demand for U.S. forces is certainly headed higher.

Mattis’s requirements reveal some surprising observations. The first surprise is the enduring utility of the aircraft carrier, at least in the eyes of commanders such as Mattis. Carrier critics point to their extravagant cost and the fact that adversary navies possess no similar capability and won’t for the foreseeable future. But the flattops remain critical to field commanders because of the risks and limitations associated with positioning comparable land-based air power at forward bases. Such deployments are often politically untenable and forward air bases are increasingly vulnerable to missile attack, problems U.S. commanders face in both the Middle East and in the Pacific. In addition to being a strong diplomatic signal, aircraft carrier deployments are frequently the only way to position reliable striking power in unstable regions.

Second, a decade of wars in Iraq and Afghanistan has conditioned observers to view the Central Command area as a region for ground forces. According to the Pentagon, 6,524 U.S. service members have been killed in the wars since 2001, almost all of them Army and Marines. Central Command was and is a ground force theater but won’t be much longer. Although infantrymen shouldered the burden in Iraq and Afghanistan, deterring and containing Iran is a job for the Navy, Air Force, and the Army’s air and missile defense units. Like the Pacific, the Central Command area is quickly turning into an air and sea power theater.

Third, Central Command’s demand for air and naval power is causing the pivot to Asia to stumble out of the starting blocks. The Obama administration’s strategic vision foresaw the Asia-Pacific as the "center of action." For military planners, the Pacific would eventually become the main effort, with all other areas relegated to a secondary "economy of force" status. Indeed, only last month, Panetta boasted in Singapore that the Pacific would get 60 percent of the Navy’s ships. But for now, it is Iran that seems to be absorbing 60 percent of the Navy’s aircraft carriers and causing Panetta to issue unsustainable deployment orders. Far from being the main effort, it is the Pacific that is the economy-of-force region. It will remain so as long as deterring Iran remains an open-ended commitment.

If we can assume a fleet of 14-15 aircraft carriers is out of the question, the Pentagon will have to find ways to get the Air Force, Marine Corps, and Army to share the burden of deterring Iran. Beyond that, the Sunni Arab countries in the Gulf Cooperation Council will have to become a more effective military alliance in order to balance Iranian power across the Persian Gulf. Until U.S. planners and diplomats get those tasks accomplished, the Pentagon will find itself propping up an overstretched and unsustainable military strategy in the Middle East and Pacific.